A transmission as taught by von Kaler et al, U.S. Pat. No. 3,812,735 includes a sliding key shift means to sequentially engage a number of speed drives between two shafts. This transmission appears in the transaxles by von Kaler et al, U.S. Pat. No. 4,103,566 and by von Kaler, U.S. Pat. No. 4,480,501.
A transaxle, U.S. Pat. No. 4,232,569 issued Nov. 11, 1980, includes a speed transmission and a generally separate range transmission to provide a wide range of speeds engaged by manipulation of two separate gearshift levers.
A transaxle by Rundle, the present Applicant, U.S. Pat. No. 4,611,504, describes a speed transmission and a more integral range transmission to provide a wide range of speeds engaged by manipulation of two separate gearshift levers. The transaxle features a unique coaxial arrangement of shafts shown here in variation of the present invention.
A copending U.S. patent continuation-in-part application Ser. No. 867,939 filed May 29, 1986, by the present Applicant, now U.S. Pat. No. 4,658,662, describes a wide range transmission controlled by a single gearshift lever and having an arrangement different than that of the present invention.
A copending U.S. patent application Ser. No. 873,365 filed June 12, 1986, by the present Applicant describes a new sliding key shift means applicable to the transmission of the present invention.
A manufacturer of small lawn tractors has developed a hybrid tractor to perform many of the tasks previously assigned only to larger and more costly garden tractors. It is imperative to retain the in-line, one lever shift convenience of the popular lawn tractors while providing the extremely slow "creep" speeds necessary for operation with rotary tillers and wide snow throwers. Currently a transaxle is utilized which employs a compromisingly small pinion for the slowest speed drive and a severe "overdrive" speed increasing drive for the fastest speed to provide a ratio range of factor ten. The small pinion must be shaft integral at increased cost and the minimal pitch diameter of the fastest speed driven gear limits the shiftshaft diameter, thus placing extra stress on the shift means. The "overdrive" ratio of the fastest speed drive also requires compensation in the form of increased and costly reduction elsewhere in the tractor drive.
The present invention describes a transmission, in variation, without limitation or compromise for use with these hybrid "super lawn tractors" and with larger garden tractors as well. These new transmissions feature greatly expanded ratio range while employing no compromisingly small pinions. The severe overdrive ratio and associated costs are eliminated so that increased countershaft diameter will strengthen the shift means and allow for coaxial shafting.